In a cellular system, wireless base terminals (WBTs) cover a wide geographic area utilizing frequency-reuse techniques. It is not uncommon for WBTs to have overlapping coverage areas to avoid null or dead spots that can cause dropped calls. In overlapping coverage areas it is possible for a mobile phone to submit a mobile origination call to a mobile telephone switching office (MTSO) by way of two or more WBTs.
In order for the MTSO to operate properly, mobile phone operators expect signals received by the MTSO to not exceed for example a maximum latency and maximum jitter. Furthermore, signals from multiple WBTs must arrive at the MTSO within a set time period in order to be identified as part of the same call stream. This time period is known as differential delay. Current mobile telephony backhaul networks are served by circuit-switched elements (e.g., T1 lines), which have very short delay since bits are transmitted at nearly the speed of light.
As telephone companies seek to reduce cost, increase features, and increase reliability, alternative backhaul technologies are being considered: Ethernet over Copper, Ethernet over Fiber, WiMAX, SONET, NG-SONET, and so on. With the growth of packet-switched (vs. circuit-switched) multi-hop backhaul, and the variability in packet delivery times, differential delay can become a significant problem for legacy MTSOs receiving WBT signals over packet-switched networks. This can be especially problematic when the packet-switched network experiences a network fault at one or more network elements carrying said messages to the MTSO.
A need therefore arises for a method and apparatus for maintaining network performance in a communication system.